QT5.3 android : QApplication::AboutToQuit() not called

I'd like to do some saving when i close my application.
In my QMainWindow, i do this :
@connect (qApp, SIGNAL(AboutToQuit()), this, SLOT(OnAboutToQuit()));@

But the slot is never called when i close the application.
I can see thanks to applicationStateChanged() that the state becomes ApplicationSuspended when i click on the Home Button. But i cannot do clean up here since i could decide to come back to the application at this point.

Would you have an idea about what is wrong and above all how to save a state before the exit ?
Thank you all!